After my '87 XJ-SC V12 fuel pump decided to quit on me last year so the car wouldn’t start, I ran a series of simple diagnostic tests. The ECU was my first guess but a friend’s XJ-S started and ran just fine with my ECU. A replacement pump relay was no help until I grounded its 87 terminal (and that mysterious orange wire) with the ignition on. While this jumper to ground enables the car to run I’m only masking the symptoms rather than curing the disease, which I’d prefer to do. The coil wires show no damage and I am at a loss where to look next. Thanx - Alan B
Oops. My Bad. That’s Pump Relay terminal 85 (not 87) - Alan B
Alan,
Pins 85 and 86 are the primary circuit (standard relay pin numbers)
Pins 30, 87 and 87a are the secondary circuit.
So if indeed the pump runs when you ground the 85 terminal then the relay is good and the fault is somewhere after that.
The ground connection from terminal 85 goes through the Start Inhibit Switch, a micro-switch mounted at the gear lever that connects to ground only when in P or N. Easy to check with a multimeter.
Other possibility is the wiring itself.
Also check that the Inertia Switch is not tripped or bad.
Hope that helps and welcome to the forum.
Aristides
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Aristides, you sir are a genius indeed. The Start Inhibit Switch (which I’d not thought of) was OK but that system needed adjusting. Once done, I turned the ignition on, removed the pump relay jumper, connected the battery and EURIKA, the fuel pump sprang to life - the sweetest sound I’ve heard from the car in quite a while.
Thanks so very much - Alan